Speaker
Description
RVA23 is ratified and the first (vendor-announced) compliant silicon is shipping, but between "the profile exists" and "userspace can rely on it" sit three unresolved kernel questions.
Discovery. Extension capability discovery between user mode and the kernel is still messy: hwprobe and prctl can disagree, so which interface should IFUNC resolvers actually trust, or does the discovery contract itself need a rethink? The "riscv: hwprobe: export the availability of vector to user" series under discussion on linux-riscv is a live example.
Dispatch. (runtime selection of optimized code paths) x86 already does coarse, library-level selection via glibc-hwcaps. Could the same mechanism sit on top of hwprobe on RISC-V, keyed on something like rva23u64? Is profile granularity even the right key? For distros like Debian that will not flip their baseline any time soon, this is probably the realistic path. But there is a catch though, as the prctl/hwprobe mismatch shows.
The hardware left behind. What compatibility fallbacks do pre-RVA23 systems get? And further out: can kernel-side cooperation support RVA23 capability certification, and what test infrastructure would that take?
Aiming at concrete next steps for the discovery contract and a dispatch story distros can adopt.